JP7081126B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire capable of suppressing the occurrence of core collapse of a bead core in a tire vulcanization molding process while reducing the weight of the tire.

In recent years, the weight of the bead portion has been reduced for the purpose of reducing the weight of the tire. As a conventional pneumatic tire relating to such a problem, the technique described in Patent Document 1 is known. In Patent Document 1, the weight of the tire is reduced by omitting the bead filler.

Japanese Unexamined Patent Publication No. 2008-149778

However, in the above-mentioned conventional pneumatic tire, there is a concern that the bead core is likely to collapse in the tire vulcanization molding process due to the omission of the bead filler.

Therefore, the present invention has been made in view of the above, and an object of the present invention is to provide a pneumatic tire capable of suppressing the occurrence of core collapse of a bead core in a tire vulcanization molding step while reducing the weight of the tire.

In order to achieve the above object, the pneumatic tire according to the present invention comprises a bead core formed by winding one or a plurality of bead wires in an annular shape and multiple times, and a single layer or a plurality of layers of rubber ply and wraps the bead core. A pneumatic tire including a carcass layer that is rewound and spanned over the bead core, and a rim cushion rubber that is arranged along the rewinding portion of the carcass layer and constitutes a rim fitting surface of the bead portion. The rewinding portion of the carcass layer contacts the main body of the carcass layer to form a closed region surrounding the bead core, and the rubber occupancy in the closed region is 15 [in a cross-sectional view in the tire meridional direction. %] The heat shrinkage rate of the carcass cord constituting the carcass ply is in the range of 0.1 [%] or more and 1.5 [%] or less, and the rubber occupancy rate is the above. Calculated as the ratio [%] of the cross-sectional area of the rubber material around the bead core in the closed area to the total cross-sectional area of the closed area, and the heat shrinkage rate of the carcass cord is the dry heat shrinkage rate in JIS L1017. It is characterized in that it is measured at a temperature of 150 ± 3 ° C. according to the test method of .

In the pneumatic tire according to the present invention, (1) the rubber occupancy in the closed region X surrounded by the main body portion and the rewinding portion of the carcass layer is set to be very low, so that there is an advantage that the tire can be made lighter. Further, (2) since the heat shrinkage rate of the carcass cord is set low, the deformation of the carcass ply due to the heat of vulcanization is suppressed in the tire vulcanization molding process, and the core collapse of the bead core is appropriately suppressed. There is.

FIG. 1 is a cross-sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a bead portion of the pneumatic tire shown in FIG. FIG. 3 is an explanatory diagram showing a carcass code of the carcass layer shown in FIG. FIG. 4 is an explanatory diagram showing a carcass code of the carcass layer shown in FIG. FIG. 5 is an enlarged view showing a rim fitting portion of the bead portion described in FIG. FIG. 6 is an explanatory diagram showing the wire arrangement structure of the bead core shown in FIG. FIG. 7 is an explanatory view showing a rim fitting portion of a bead portion in a tire rim assembled state. FIG. 8 is an explanatory view showing the rim fitting portion shown in FIG. FIG. 9 is an explanatory view showing the rim fitting portion shown in FIG. FIG. 10 is an explanatory diagram showing a modified example of the bead core shown in FIG. FIG. 11 is an explanatory diagram showing a modified example of the bead core shown in FIG. FIG. 12 is an explanatory diagram showing a modified example of the bead core shown in FIG. FIG. 13 is an explanatory diagram showing a modified example of the bead core shown in FIG. FIG. 14 is an explanatory diagram showing a modified example of the bead core shown in FIG. FIG. 15 is an enlarged view showing a tire side portion of the pneumatic tire shown in FIG. FIG. 16 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment of the present invention. FIG. 17 is an explanatory diagram showing a bead core of a conventional test tire.

Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment. In addition, the components of this embodiment include those that are replaceable and self-explanatory while maintaining the identity of the invention. Further, the plurality of modifications described in this embodiment can be arbitrarily combined within the range of those skilled in the art.

[Pneumatic tires]
FIG. 1 is a cross-sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. The figure shows a cross-sectional view of a one-sided region in the tire radial direction. Further, the figure shows a radial tire for a passenger car as an example of a pneumatic tire.

In the figure, the cross section in the tire meridian direction means a cross section when the tire is cut on a plane including the tire rotation axis (not shown). Further, the reference numeral CL is a tire equatorial plane, and refers to a plane that passes through the center point of the tire in the direction of the tire rotation axis and is perpendicular to the tire rotation axis. Further, the tire width direction means a direction parallel to the tire rotation axis, and the tire radial direction means a direction perpendicular to the tire rotation axis.

The pneumatic tire 1 has an annular structure centered on a tire rotation axis, and has a pair of bead cores 11 and 11, a carcass layer 13, a belt layer 14, a tread rubber 15, and a pair of sidewall rubbers 16 and 16. , A pair of rim cushion rubbers 17 and 17, and an inner liner 18 (see FIG. 1).

The pair of bead cores 11 and 11 are formed by winding one or a plurality of bead wires made of steel in an annular shape and multiple times, and are embedded in the bead portion to form the cores of the left and right bead portions.

The carcass layer 13 has a single-layer structure composed of one carcass ply or a multi-layer structure formed by laminating a plurality of carcass plies, and is bridged between the left and right bead cores 11 and 11 in a toroidal shape to form a tire skeleton. To configure. Further, both ends of the carcass layer 13 are wound and locked outward in the tire width direction so as to wrap the bead core 11. Further, the carcass ply of the carcass layer 13 is formed by coating a plurality of carcass cords made of a predetermined organic fiber material with coated rubber and rolling them, and has a carcass angle of 80 [deg] or more and 90 [deg] or less in absolute value. (Defined as the longitudinal tilt angle of the carcass cord with respect to the tire circumferential direction). In the configuration of FIG. 1, the carcass layer 13 has a single-layer structure composed of a single carcass ply, but the present invention is not limited to this, and the carcass layer 13 has a multi-layer structure in which a plurality of carcass plies are laminated. Also good (not shown). The details of the carcass ply will be described later.

The belt layer 14 is formed by laminating a pair of crossing belts 141 and 142, a belt cover 143 and a pair of belt edge covers 144, and is arranged so as to be hung around the outer periphery of the carcass layer 13. The pair of crossed belts 141 and 142 are formed by coating a plurality of belt cords made of steel or organic fiber with coated rubber and rolling them, and have a belt angle of 20 [deg] or more and 55 [deg] or less in absolute value. Have. The belt angles of the cross belts 141 and 142 are not limited to the above range and can be set arbitrarily. Further, the pair of crossing belts 141 and 142 have differently signed belt angles (defined as the inclination angle of the belt cord in the longitudinal direction with respect to the tire circumferential direction), and the longitudinal directions of the belt cords intersect each other. (So-called cross-ply structure). The belt cover 143 and the pair of belt edge covers 144 are configured by coating a belt cover cord made of steel or an organic fiber material with a coated rubber, and have a belt angle of 0 [deg] or more and 10 [deg] or less in absolute value. Further, the belt cover 143 and the pair of belt edge covers 144 are strip materials formed by coating one or a plurality of belt cover cords with coated rubber, and the strip materials are applied to the outer peripheral surfaces of the cross belts 141 and 142. On the other hand, it is configured by winding it in a spiral shape multiple times in the tire circumferential direction. The belt cover 143 and the pair of belt edge covers 144 may be omitted (not shown).

The tread rubber 15 is arranged on the outer periphery of the carcass layer 13 and the belt layer 14 in the radial direction of the tire to form a tread portion of the tire. The pair of sidewall rubbers 16 and 16 are arranged on the outer sides of the carcass layer 13 in the tire width direction, respectively, to form the left and right sidewall portions. The pair of rim cushion rubbers 17 and 17 are arranged inside the left and right bead cores 11 and 11 and the rewinding portion of the carcass layer 13 in the tire radial direction, respectively, to form a rim fitting surface of the bead portion.

The inner liner 18 is an air permeation prevention layer arranged on the inner surface of the tire and covering the carcass layer 13, suppresses oxidation due to exposure of the carcass layer 13, and prevents leakage of air filled in the tire. Further, the inner liner 18 is composed of, for example, a rubber composition containing butyl rubber as a main component, a thermoplastic resin, a thermoplastic elastomer composition in which an elastomer component is blended with the thermoplastic resin, and the like. Further, the inner liner 18 is adhered to the carcass layer 13 via a tie rubber (not shown).

[Bead fillerless structure]
FIG. 2 is a cross-sectional view showing a bead portion of the pneumatic tire shown in FIG. The figure shows a cross-sectional view of the bead portion in the tire meridian direction in the state before the tire rim is assembled.

As shown in FIG. 2, the carcass layer 13 is wound and locked outward in the tire width direction so as to wrap around the bead core 11. At this time, when the rewinding portion 132 of the carcass layer 13 comes into contact with the main body portion 131, a closed region X surrounding the bead core 11 is formed. Further, since the closed region X is continuous over the entire circumference of the tire, an annular closed space surrounding the bead core 11 is formed.

The closed region X is defined as a region surrounded by the carcass ply of the carcass layer 13 in a cross-sectional view in the tire meridian direction. Specifically, the region surrounded by the surface of the coated rubber of the carcass ply becomes the boundary line of the closed region X.

Further, in the configuration of FIG. 2, the carcass layer 13 is composed of a single layer of carcass ply, and the closed region X is formed by the self-contact of the carcass ply. On the other hand, in a configuration consisting of a plurality of carcass plies on which the carcass layers 13 are laminated (not shown), the closed region X may be formed by mutual contact of different carcass plies. For example, the carcass layer 13 has a two-layer structure in which the first and second carcass plies are laminated, and the radial height H1 of the bead core 11 without the rewinding portion of the first carcass ply coming into contact with the main body portion. It is assumed that the winding portion of the second carcass ply extends to the outside in the radial direction of the bead core 11 and comes into contact with the main body portion of the first carcass ply (not shown). The diameter.

At this time, the rubber occupancy in the closed region X is preferably in the range of 15 [%] or less, more preferably in the range of 10 [%] or less, and more preferably in the range of 5 [%] or less. More preferred. Therefore, the rubber occupancy in the closed region X surrounded by the main body 131 and the rewinding portion 132 of the carcass layer 13, that is, the rubber volume around the bead core 11 is set very low. As a result, the purpose of reducing the weight of the tire by omitting the bead filler is achieved. The lower limit of the rubber occupancy rate is not particularly limited, but is preferably 0.1 [%] or more.

The rubber occupancy rate is calculated as the ratio [%] of the cross-sectional area of the rubber material in the closed area X to the total cross-sectional area of the closed area X in the cross-sectional view in the tire meridian direction.

For example, in the configuration of FIG. 2, the rewinding portion 132 of the carcass layer 13 is rewound without including the bead filler in the closed region X and is in contact with the main body portion 131. Further, the carcass ply of the carcass layer 13 is wound up along the outer peripheral surface of the bead core 11. Therefore, only the constituent members of the bead core 11 exist in the closed region X. The components of the bead core 11 include a bead wire 111, an insulation rubber, a bead cover and a wrapping thread.

The bead filler is a reinforcing rubber that is sandwiched between the main body portion and the rewinding portion of the carcass layer and is arranged to increase the rigidity of the bead portion. Further, the bead filler generally has a triangular cross section and has a rubber hardness of 65 or more and 99 or less.

Rubber hardness is measured according to JIS K6253.

Further, in the configuration in which the bead filler is omitted, as shown in FIG. 2, it is preferable that the rewinding portion 132 of the carcass layer 13 is in surface contact with the main body portion 131 of the carcass layer 13 and is locked. Further, the radial height H2 of the contact portion between the main body portion 131 and the rewinding portion 132 of the carcass layer 13 has a relationship of 0.80 ≦ H2 / H1 ≦ 3.00 with respect to the radial height H1 of the bead core 11. It is preferable to have a relationship of 1.20 ≦ H2 / H1 ≦ 2.50, and it is more preferable to have a relationship of 1.20 ≦ H2 / H1 ≦ 2.50. As a result, the radial height H2 of the self-contact portion of the carcass layer 13 is optimized. That is, by the above lower limit, the rewinding portion 132 stably contacts the main body portion 131, the deformation of the carcass ply in the tire vulcanization molding step is suppressed, and the stress acting on the bead core 11 is reduced. As a result, the core collapse of the bead core 11 is appropriately suppressed, and the rim fitability of the tire is improved. Further, the upper limit suppresses an increase in tire weight due to an excessive rewinding portion 132.

The radial height H1 of the bead core is the outermost layer in the tire radial direction and the tire width direction from the inner end in the tire radial direction of the innermost layer in the tire radial direction and the outermost wire cross section in the tire width direction in the wire arrangement structure of the bead core. Measured as the maximum tire radial height to the tire radial outer end of the outermost wire cross section of.

The radial height H2 of the self-contact portion of the carcass layer is measured as the maximum length in the tire radial direction of the contact portion between the main body portion and the rewinding portion of the carcass layer.

Further, in the above configuration, as shown in FIG. 2, it is preferable that the end portion (reference numeral omitted in the drawing) of the rewinding portion 132 of the carcass layer 13 contacts the main body portion 131 of the carcass layer 13. In such a configuration, the stress concentration at the end portion of the rewinding portion 132 is relaxed as compared with the configuration in which the end portion of the rewinding portion 132 is separated from the main body portion 131 (not shown). As a result, the separation of the peripheral rubber starting from the end of the rewinding portion 132 is suppressed.

Further, the actual length La2 of the contact portion between the main body portion 131 and the rewinding portion 132 of the carcass layer 13 (dimension symbol omitted in the figure) is relative to the peripheral length La1 (dimension symbol omitted in the figure) of the closed region X. , 0.30 ≦ La2 / La1 ≦ 2.00, more preferably 0.37 ≦ La2 / La1 ≦ 1.80. As a result, the actual length La2 of the self-contact portion of the carcass layer 13 is optimized. That is, by the above lower limit, the spring characteristics of the carcass layer 13 are properly secured, and the steering stability on a dry road surface is ensured. Further, the actual length La2 of the self-contact portion of the carcass layer 13 is secured, the deformation of the carcass ply in the tire vulcanization molding step is suppressed, and the core collapse of the bead core 11 is appropriately suppressed. Further, the upper limit suppresses an increase in tire weight due to an excessive rewinding portion 132.

The peripheral length La1 of the closed region X is measured as the periphery length of the surface of the carcass ply constituting the boundary line of the closed region X in a cross-sectional view in the tire meridian direction.

The actual length La2 of the contact portion is measured as the periferi length at the self-contact portion between the main body portion and the rewinding portion of the carcass layer in a cross-sectional view in the tire meridian direction.

[Heat shrinkage of carcass cord]
In the configuration in which the bead filler is omitted as described above, there is a concern that the bead core is likely to collapse in the tire vulcanization molding process. When the bead core collapses, the function of the bead core deteriorates and the rim fit of the tire deteriorates. Therefore, in this pneumatic tire 1, the following configuration is adopted in order to suppress the occurrence of core collapse of the bead core in the tire vulcanization molding process.

3 and 4 are explanatory views showing the carcass code of the carcass layer shown in FIG. 1. In these figures, FIG. 3 shows a radial cross-sectional view of the carcass cord 130, which is a single component, and FIG. 4 shows a strong elongation curve of the carcass cord 130.

As described above, the carcass layer 13 is composed of a single layer or a plurality of layers of carcass ply, and the carcass ply covers a plurality of carcass cords 130 (see FIG. 3) made of a predetermined organic fiber material with coated rubber (not shown). It is composed by rolling.

At this time, the heat shrinkage of the carcass cord 130 is preferably in the range of 0.1 [%] or more and 1.5 [%] or less, and preferably in the range of 0.2 [%] or more and 1.2 [%] or less. It is more preferably in the range of 0.4 [%] or more and 1.0 [%] or less. That is, the heat shrinkage rate of the carcass cord 130 is set to be very low as compared with the carcass cord made of general nylon fiber or polyester fiber.

For example, in the conventional carcass cord sample, the heat shrinkage rate when two nylon lower-twisted yarns composed of nylon 66 fiber bundles having a fineness of 940 [dtex] are top-twisted is 2.5 [%], and the fineness is 1400. The heat shrinkage rate when two nylon bottom-twisted yarns made of [dtex] nylon 66 fiber bundles were top-twisted was 2.4 [%]. Further, the heat shrinkage rate when two polyester lower twisted yarns composed of a polyethylene terephthalate fiber bundle having a fineness of 1100 [dtex] is top-twisted is 2.3 [%], and the polyethylene terephthalate having a fineness of 1670 [dtex] is obtained. The heat shrinkage rate when two polyester bottom twisted yarns composed of fiber bundles were top-twisted was 2.2 [%].

The heat shrinkage of the carcass cord is measured according to the dry heat shrinkage test method in JIS L1017.

In the above configuration, the heat shrinkage rate of the carcass cord 130 is optimized. That is, since the heat shrinkage rate of the carcass cord 130 is set low by the above upper limit, the deformation of the carcass ply due to the vulcanization heat is suppressed in the tire vulcanization molding step, and the stress acting on the bead core 11 is reduced. Sulfur. As a result, the core collapse of the bead core 11 is appropriately suppressed, and the rim fitability of the tire is improved. Further, by the above lower limit, the fibrilization of the carcass code 130 is suppressed, and the durability of the carcass ply is ensured.

As the carcass cord 130 having the above-mentioned heat shrinkage rate, for example, a composite yarn made of aramid fiber and polyester fiber (so-called hybrid carcass cord) can be adopted. Specifically, the carcass cord 130 may be a composite yarn formed by top-twisting a plurality of aramid lower twist yarns composed of aramid fiber bundles and at least one polyester lower twist yarn composed of polyester fiber bundles. preferable. Further, as the aramid fiber, for example, an aromatic polyamide fiber can be adopted. As the polyester fiber, for example, polyethylene terephthalate (PET) fiber and polyethylene naphthalate (PEN) fiber can be adopted.

In such a configuration, the amount of yarn can be reduced as compared with, for example, a carcass cord made of only polyester fibers, so that the cord diameter of the carcass cord 130 can be reduced. As a result, the gauge of the carcass ply can be thinned while reducing the heat shrinkage rate of the carcass cord 130. Further, for example, as compared with the carcass cord made of only aramid fiber, the fibrilization of the carcass cord 130 is suppressed, and the durability of the carcass ply is ensured.

Not limited to the above, for example, the carcass cord 130 may be configured by top-twisting three or more aramid lower twisted yarns 1301 and one or two polyester lower twisted yarns 1302 (not shown). The upper limit of the number of these lower twisted yarns is not particularly limited, but is restricted in relation to the cord diameter and the like described later.

When the carcass cord 130 is a composite yarn made of aramid fiber and polyester fiber, the fineness of the aramid lower twisted yarn is in the range of 400 [dtex] or more and 1200 [dtex] or less, and the fineness of the polyester lower twisted yarn is high. It is preferable that the total fineness D of the composite yarn is in the range of 500 [dtex] or more and 1200 [dtex] or less, and the total fineness D of the composite yarn is in the range of 1000 [dtex] or more and 2400 [dtex] or less. As a result, the total fineness of each lower twisted yarn constituting the carcass cord 130 and the total fineness D of the composite yarn are optimized. That is, the strength of the carcass cord is ensured by the above lower limit, and the weight reduction of the carcass ply is ensured by the above upper limit.

The total fineness of the lower twisted yarn and the total fineness D of the composite yarn are calculated as the total fineness of each twisted yarn. For a single lower twisted yarn, its fineness is the total fineness.

Further, it is preferable that the twist coefficient K of the composite yarn is in the range of 2000 or more and 2400 or less. As a result, the twist coefficient K of the composite yarn constituting the carcass cord is optimized. That is, the fatigue resistance of the carcass cord is ensured by the above lower limit. In addition, the above upper limit suppresses damage to the carcass ply.

The twist coefficient K of the composite yarn is calculated by the following mathematical formula (2). In the same formula, T is the number of upper twists [times / 10 cm] of the composite yarn, D1 is the total fineness [dtex] of the first lower twist, ρ1 is the specific density of the first lower twist, and D2 is. It is the total fineness [dtex] of the second lower twisted yarn, and ρ2 is the specific gravity of the second lower twisted yarn.

K = T · (D1 / ρ1 + D2 / ρ2) ^1/2 ... (2)

Further, the cord diameter of the carcass code 130 is preferably in the range of 0.30 [mm] or more and 0.55 [mm] or less, and is in the range of 0.33 [mm] or more and 0.52 [mm] or less. More preferably, it is more preferably in the range of 0.40 [mm] or more and 0.50 [mm] or less. As a result, the function of the carcass cord 130 is ensured, and the carcass ply is thinned and has a pressure resistance.

The cord diameter is measured as the diameter of the circumscribed circle in the radial cross-sectional view of the cord when the cord is made of a composite yarn.

Further, the intermediate elongation of the carcass code 130 is preferably in the range of 1.0 [%] or more and 10 [%] or less, and more preferably in the range of 1.3 [%] or more and 6 [%] or less. It is preferably in the range of 2.0 [%] or more and 5 [%] or less. As a result, the function of the carcass cord 130 is ensured, and the carcass ply is thinned and has a pressure resistance.

The intermediate elongation is measured according to the test method of elongation under constant load in JIS L1017.

Further, the number of ends of the carcass code 130 is preferably in the range of 35 [lines / 50 mm] or more and 85 [lines / 50 mm] or less, and is in the range of 45 [lines / 50 mm] or more and 80 [lines / 50 mm] or less. More preferably, it is more preferably in the range of 60 [lines / 50 mm] or more and 77 [lines / 50 mm] or less. As a result, the function of the carcass cord 130 is ensured, and the carcass ply is thinned and has a pressure resistance.

For example, in FIGS. 3 and 4, the composite yarn Y (Carcass cord 130) shown in FIG. 3 has two aramid lower twist yarns 1301 and 1301 composed of an aromatic polyamide fiber bundle having a fineness of 440 [dtex] and a fineness of 560 [. dtex] is configured by twisting one polyester bottom plying 1302 made of a polyethylene terephthalate fiber bundle in the direction opposite to the twisting direction of the bottom twisted yarns 1301 and 1302. Further, the total fineness D of the composite yarn Y is 1440 [dtex], and the twist coefficient K is 2300. Further, the cord diameter of the carcass cord 130 is 0.46 [mm], and the intermediate elongation is 2.0 [%]. Further, in FIG. 4, the carcass cord 130 of Examples A and B is composed of the above-mentioned composite yarn Y. Further, in Example A, the intermediate elongation is 2.9 [%] and the number of ends is 70 [lines / 50 mm], and in Example B, the intermediate elongation is 2.0 [%] and the number of ends is 77 [lines / 50 mm]. ].

On the other hand, the conventional carcass cord of FIG. 4 is composed of two polyester lower twisted yarns made of a polyethylene terephthalate fiber bundle having a fineness of 1670 [dtex] and twisted upward. Further, the cord diameter of the carcass cord is 0.69 [mm], and the intermediate elongation is 5.0 [%].

As shown in FIG. 4, it can be seen that the carcass cords of Examples A and B have lower elongation and higher strength than the conventional examples.

The cord-coated rubber of the carcass layer 13 is, for example, one or a plurality of types of rubber selected from natural rubber (NR), styrene-butadiene rubber (SBR), butadiene rubber (BR), and isoprene rubber (IR). Can be used. Further, these rubbers are terminal-modified with a functional group containing elements such as nitrogen, oxygen, fluorine, chlorine, silicon, phosphorus or sulfur, for example, amine, amide, hydroxyl, ester, ketone, syroxy or alkylsilyl. Alternatively, one end-modified with epoxy can be used. The carbon black blended in these rubbers has, for example, an iodine adsorption amount of 20 to 100 [g / kg], preferably 20 to 50 [g / kg], and a DBP absorption amount of 50 to 135 [cm3 / 100 g]. , Preferably 50 to 100 [cm3 / 100 g], and a CTAB adsorption specific surface area of 30 to 90 [m2 / g], preferably 30 to 45 [m2 / g] can be used. The amount of sulfur used is, for example, 1.5 to 4.0 parts by mass, preferably 2.0 to 3.0 parts by mass with respect to 100 parts by mass of rubber.

[Outer reinforcement rubber]
As shown in FIG. 2, the pneumatic tire 1 includes an outer reinforcing rubber 19 in addition to the sidewall rubber 16 and the rim cushion rubber 17 described above.

As described above, the sidewall rubbers 16 are arranged on the outer sides of the carcass layer 13 in the tire width direction to form the sidewall portion of the tire. Further, the rubber hardness of the sidewall rubber 16 is in the range of 40 or more and 70 or less. Further, the breaking elongation of the sidewall rubber 16 is in the range of 400 [%] or more and 650 [%] or less.

Break elongation is measured in accordance with JIS K6251 regulations.

As described above, the rim cushion rubber 17 is arranged inside the rewinding portion 132 of the bead core 11 and the carcass layer 13 in the tire radial direction to form the rim fitting surface of the bead portion. Further, the rubber hardness of the rim cushion rubber 17 is in the range of 50 or more and 80 or less. Further, the breaking elongation of the rim cushion rubber 17 is in the range of 150 [%] or more and 450 [%] or less.

The outer reinforcing rubber 19 is sandwiched and arranged between the rewinding portion 132 of the carcass layer 13 and the rim cushion rubber 17 (see FIG. 2). In such a configuration, in particular, in a configuration in which the above-mentioned bead filler is omitted, the spring characteristics of the bead portion are reinforced by the outer reinforcing rubber 19, and steering stability on a dry road surface is ensured.

Further, the rubber hardness of the outer reinforcing rubber 19 is preferably in the range of 65 or more and 105 or less, and more preferably in the range of 70 or more and 100 or less. As a result, the above-mentioned action of the outer reinforcing rubber 19 is properly ensured.

Further, the rubber hardness of the outer reinforcing rubber 19 is higher than the rubber hardness of the sidewall rubber 16 and the rim cushion rubber 17. Specifically, the difference ΔHs_SW between the rubber hardness of the sidewall rubber 16 and the rubber hardness of the outer reinforcing rubber 19 is preferably 7 or more, and more preferably 12 or more. Further, the difference ΔHs_RC between the rubber hardness of the rim cushion rubber 17 and the rubber hardness of the outer reinforcing rubber 19 is preferably 3 or more, and more preferably 7 or more. As a result, the effect of reinforcing the spring characteristics of the bead portion by the outer reinforcing rubber 19 is properly exhibited. The lower limit of the difference ΔHs_SW in the rubber hardness is restricted by the lower limit of the rubber hardness of the outer reinforcing rubber 19.

Further, the breaking elongation of the outer reinforcing rubber 19 is preferably in the range of 50 [%] or more and 400 [%] or less, and more preferably in the range of 70 [%] or more and 350 [%] or less.

For example, in the configuration of FIG. 2, the rim cushion rubber 17 extends from the bead to Bt over the entire area of the bead base Bb to form a rim fitting surface of the rim 10 with respect to the bead sheet 101. Further, the rim cushion rubber 17 extends from the bead base Bb along the rewinding portion 132 of the carcass layer 13 outward in the tire radial direction to form a fitting surface of the rim 10 with respect to the flange 102. Further, the tire radial outer end portion of the rim cushion rubber 17 is inserted between the carcass layer 13 and the sidewall rubber 16, and the end portion of the rewinding portion 132 of the carcass layer 13 and the flange 102 of the rim 10. Also extends to the outside in the radial direction of the tire. Further, the bead portion may be provided with a chafer (not shown).

The rim cushion rubber 17 preferably extends from the bead heel Bh to the central portion of the innermost layer of the bead core 11 in the tire radial direction (midpoint Cm described later). As a result, the durability of the rim fitting portion of the bead portion is properly ensured.

Further, in the configuration of FIG. 2, the outer reinforcing rubber 19 has a long shape in the tire radial direction and is sandwiched between the rewinding portion 132 of the carcass layer 13 and the rim cushion rubber 17. Further, the inner end portion of the outer reinforcing rubber 19 in the tire radial direction overlaps the bead core 11 in the tire radial direction. Further, the outer reinforcing rubber 19 extends beyond the end portion of the rewinding portion 132 of the carcass layer 13 to the outside in the tire radial direction, and is sandwiched between the main body portion 131 of the carcass layer 13 and the sidewall rubber 16. .. Further, the outer reinforcing rubber 19 covers the end portion of the rewinding portion 132 of the carcass layer 13 from the outside in the tire width direction. Further, the outer reinforcing rubber 19 is adjacent to the rewinding portion 132 of the carcass layer 13 over the entire contact portion between the main body portion 131 of the carcass layer 13 and the rewinding portion 132. As a result, the spring characteristics of the bead portion are appropriately reinforced by the outer reinforcing rubber 19, the steering stability on the dry road surface is improved, and the durability of the bead portion is improved. Further, since the rubber hardness of the outer reinforcing rubber 19 is higher than the rubber hardness of the sidewall rubber 16 and the rim cushion rubber 17, the distribution of the rubber hardness in the vicinity of the end portion of the rewinding portion 132 of the carcass layer 13 is the carcus layer 13. It decreases from the end of the rubber toward the surface of the tire side. As a result, the stress generated near the end of the carcass layer 13 is relaxed, and the separation of the peripheral rubber is suppressed.

Further, the radial height H3 from the measurement point of the tire inner diameter RD to the tire radial outer end of the outer reinforcing rubber 19 and the tire cross-sectional height SH (see FIG. 1) are 0.10 ≦ H3 / SH. It is preferable to have a relationship of ≦ 0.60, and more preferably to have a relationship of 0.15 ≦ H3 / SH ≦ 0.50. As a result, the radial height H3 of the outer reinforcing rubber 19 is optimized. That is, according to the above lower limit, the spring characteristics of the bead portion are appropriately reinforced by the outer reinforcing rubber 19, the steering stability on the dry road surface is improved, and the durability of the bead portion is improved. Further, the upper limit suppresses an increase in tire weight due to an excessive amount of the outer reinforcing rubber 19.

The tire inner diameter RD is equal to the rim diameter of the specified rim.

The radial height H3 is measured as a no-load state while the tire is mounted on the specified rim to apply the specified internal pressure. Specifically, it is calculated as the difference between the diameter of the outer end portion of the outer reinforcing rubber 19 in the tire radial direction and the tire inner diameter RD.

The tire cross-sectional height SH is a distance of ½ of the difference between the tire outer diameter and the rim diameter, and is measured as a no-load state while the tire is mounted on the specified rim to apply the specified internal pressure.

The specified rim means the "applicable rim" specified in JATMA, the "Design Rim" specified in TRA, or the "Measuring Rim" specified in ETRTO. The specified internal pressure means the "maximum air pressure" specified in JATTA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified in TRA, or "INFLATION PRESSURES" specified in ETRTO. The specified load means the "maximum load capacity" specified in JATTA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified in TRA, or the "LOAD CAPACITY" specified in ETRTO. However, in JATTA, in the case of a passenger car tire, the specified internal pressure is an air pressure of 180 [kPa], and the specified load is 88 [%] of the maximum load capacity.

Further, the radial height H4 from the end of the rewinding portion 132 of the carcass layer 13 to the radial outer end of the outer reinforcing rubber 19 is the contact portion between the main body portion 131 of the carcass layer 13 and the rewinding portion 132. It is preferable to have a relationship of 0.10 ≦ H4 / H2 with respect to the radial height H2, and it is more preferable to have a relationship of 0.30 ≦ H4 / H2. As a result, the steering stability on a dry road surface is improved, and the durability of the bead portion is improved. The upper limit of the ratio H4 / H2 is restricted by the above-mentioned upper limit of the ratio H3 / SH.

Further, the tire radial overlap amount H5 between the outer reinforcing rubber 19 and the bead core 11 may have a relationship of 0.05 ≦ H5 / H1 ≦ 1.00 with respect to the radial height H1 of the bead core 11. It is preferable to have a relationship of 0.10 ≦ H5 / H1 ≦ 1.00. Further, it is preferable that the overlap amount H5 is in the range of 5.0 [mm] ≦ H5. As a result, the overlap amount H5 between the outer reinforcing rubber 19 and the bead core 11 is optimized. In particular, by the above lower limit, the overlap amount H5 is secured, and the separation of the rubber at the inner end portion of the outer reinforcing rubber 19 in the tire radial direction is suppressed. However, the present invention is not limited to this, and the outer reinforcing rubber 19 may be arranged outside the bead core 11 in the tire radial direction (not shown).

The overlap amount H5 is measured as a no-load state while the tire is mounted on the specified rim to apply the specified internal pressure.

Further, the length T1 of the vertical line drawn from the end of the rewinding portion 132 of the carcass layer 13 to the outer surface of the tire side portion and the thickness T2 of the outer reinforcing rubber 19 on the vertical line are 0.10 ≦ T2 /. It is preferable to have a relationship of T1 ≦ 0.90, and more preferably to have a relationship of 0.20 ≦ T2 / T1 ≦ 0.80. As a result, the thickness T2 of the outer reinforcing rubber 19 is optimized. That is, according to the above lower limit, the spring characteristics of the bead portion are appropriately reinforced by the outer reinforcing rubber 19, the steering stability on the dry road surface is improved, and the durability of the bead portion is improved. Further, the upper limit suppresses an increase in tire weight due to an excessive amount of the outer reinforcing rubber 19.

Further, in the configuration provided with the outer reinforcing rubber 19 instead of the bead filler as described above, the numerical value K defined by the following mathematical formula (1) is preferably 0.17 ≦ K, and 0.20 ≦ K. Is more preferable. As a result, the function of the outer reinforcing rubber 19 is properly ensured. In formula (1), W is the tire nominal width [mm], I is the tire nominal inner diameter [inch], and B is the total cross-sectional area of the bead wire in the bead core [mm ² ].

In the configuration of FIG. 2, the outer reinforcing rubber 19 is arranged in the bead portion as described above. However, the present invention is not limited to this, and when the above-mentioned numerical value K is less than 0.40, the outer reinforcing rubber 19 may be omitted. For example, the rim cushion rubber 17 may have a thick-walled structure and may be arranged so as to fill the arrangement area of the outer reinforcing rubber 19 in FIG. 2 (not shown).

[Change rate of rim fitting part]
In the configuration in which the bead filler is omitted as described above, the rigidity of the bead portion tends to decrease, and the rim fitting pressure of the bead portion tends to decrease. Therefore, in the configuration of FIG. 2, the bead core 11 has the following configuration in order to ensure the rim fitability of the tire.

FIG. 5 is an enlarged view showing a rim fitting portion of the bead portion described in FIG. FIG. 6 is an explanatory diagram showing the wire arrangement structure of the bead core shown in FIG. FIG. 7 is an explanatory view showing a rim fitting portion of a bead portion in a tire rim assembled state. In these figures, FIG. 5 shows a rim fitting portion in a state before rim assembly, and FIG. 7 shows a rim fitting portion in a state after rim assembly. Further, FIG. 6 shows a radial cross-sectional view of the unvulcanized bead core 11 at the time of a single component.

In FIG. 2, the rim fitting surface of the bead portion includes a bead base Bb, a bead to Bt, and a bead heel Bh, and has a uniform contour shape in the tire circumferential direction. The bead base Bb is a flat region formed inside the bead portion in the radial direction of the tire, and constitutes a contact surface of the rim with respect to the bead sheet 101. The bead to Bt is the tip of a bead portion having an L-shape or a V-shape in a cross-sectional view in the tire meridian direction, and is located on the innermost side in the tire width direction of the rim fitting surface. The bead heel Bh is a bent portion connecting the wall surface of the tire side portion and the bead base Bb.

Before assembling the tire rim (see Fig. 2 and Fig. 5), the position of the left and right bead parts is the specified rim width and rim diameter measurement when the tire unit is upright with the tire rotation axis horizontal. It is defined as the state when it is fixed so as to match the point. Such a tire shape is closest to the tire shape in the tire vulcanization mold, that is, the natural tire shape before inflating.

The state after the tire is assembled to the rim (see FIG. 7) is defined as the state when the tire is mounted on the specified rim, the specified internal pressure is applied, and the tire is in a no-load state. In the rim-assembled state of the tire, the rim fitting surface of the bead portion is fitted to the rim 10 of the wheel, and the tire is held. At this time, the bead base Bb on the rim fitting surface is pressed against the bead sheet 101 of the rim 10 and comes into surface contact with each other, so that the fitting portion between the bead portion and the rim 10 is sealed and the airtightness inside the tire is improved. Is secured. Further, the bead heel Bh is located at the connection portion between the bead sheet 101 and the flange 102, the region outside the bead heel Bh of the rim fitting surface abuts on the flange 102 of the rim 10, and the bead portion is the tire width. It is held from the outside in the direction.

As shown in FIG. 6, the bead core 11 has a predetermined wire arrangement structure in which the wire cross sections of the bead wires 111 are arranged in a cross-sectional view in the tire meridian direction. This wire arrangement structure will be described later.

Here, in a cross-sectional view in the tire meridional direction in the state before the tire is assembled to the rim (see FIG. 5), the innermost layer in the tire radial direction and the innermost and outermost wires in the tire width direction in the wire arrangement structure of the bead core 11. A tangent line L1 that is in contact with the cross section from the rim fitting surface side is defined. Further, the contacts C1 and C2 of the tangent line L1 for each wire cross section and the midpoint Cm of these contacts C1 and C2 are defined, respectively. Further, gauges G1, G2 and Gm in the tire radial direction from the contacts C1, C2 and the midpoint Cm to the rim fitting surface are defined. Specifically, in the cross-sectional view in the tire meridional direction, the intersection points P1, P2 and Pm of the bead base Bb and the straight line passing through the contacts C1, C2 and the midpoint Cm and perpendicular to the tire axis direction are drawn, and the contacts are contacted. The distance between C1, C2 and the midpoint Cm and the intersections P1, P2 and Pm is measured as gauges G1, G2 and Gm.

Similarly, gauges G1', G2' and Gm'of the rim fitting portion in the state after the tire is assembled to the rim (see FIG. 7) are defined.

At this time, it is preferable that the rate of change ΔG1, ΔG2, ΔGm of the gauges G1, G2, and Gm of the rim fitting portion before and after the rim assembly is in the range of 10 [%] or more and 60 [%] or less, respectively. It is more preferably in the range of [%] or more and 50 [%] or less, further preferably in the range of 20 [%] or more and 45 [%] or less, and in the range of 25 [%] or more and 40 [%] or less. Most preferably. Therefore, the rate of change ΔG1, ΔG2, ΔGm of the gauges G1, G2, and Gm is set to be larger than that of a general tire structure having a bead filler. As a result, the rate of change ΔG1, ΔG2, and ΔGm of the rim fitting portion is optimized. That is, the rim fitting pressure is secured by the above lower limit, and the rim fitting property of the tire is ensured. Further, the above upper limit suppresses deterioration of tire rim assembly workability due to excessive rim fitting pressure.

The rate of change ΔGi is defined as ΔGi = (Gi-Gi') / Gi × 100 using the gauges Gi and gauge Gi'before and after rim assembly at a predetermined measurement point. For example, the rate of change ΔG1 is calculated as ΔG1 = (G1-G1') / G1 × 100 using the gauge G1 before rim assembly (see FIG. 5) and the gauge G1'after rim assembly (see FIG. 7). Ru.

The rate of change ΔG1, ΔG2, and ΔGm of the rim fitting portion described above is realized by, for example, the configuration of the cushion rubber layer 20 (see FIG. 8) and the configuration of the taper angle of the bead base Bb (see FIG. 9), which will be described later. ..

Further, it is preferable that the rate of change ΔG1, ΔG2, ΔGm of the rim fitting portion satisfies the condition | ΔGm-ΔG2 | << | ΔG1-ΔGm |. Therefore, the change rate difference | ΔG1-ΔGm | on the bead to Bt side is set to be larger than the change rate difference | ΔGm−ΔG2 | on the bead heel Bh side. Specifically, it is preferable that the rate of change ΔG1, ΔG2, ΔGm satisfies the condition of 20 [%] ≦ | (ΔG1-ΔGm) / (ΔGm−ΔG2) | ≦ 450 [%], and 30 [%] ≦ | (ΔG1-ΔGm) / (ΔGm−ΔG2) | It is more preferable to satisfy the condition of ≦ 300 [%]. As a result, the relationship between the rate of change ΔG1, ΔG2, and ΔGm of the rim fitting portion is optimized. That is, the above lower limit improves the rim fitability of the tire. Further, the above upper limit improves the workability of tire rim assembly.

Further, it is preferable that the rate of change ΔG1, ΔG2, ΔGm of the gauges G1, G2 and Gm of the rim fitting portion has a relationship of ΔG2 <ΔGm <ΔG1. That is, the rate of change ΔG1, ΔG2, ΔGm increases toward the bead to Bt side. This improves the rim fit of the tire.

Further, in the configuration of FIG. 3, the gauges G1, G2 and Gm of the rim fitting portion in the state before the rim assembly of the tire have a relationship of G2 <Gm <G1. That is, the gauges G1, G2 and Gm of the rim fitting portion increase toward the bead to Bt side. As a result, the interrelationship between the rate of change ΔG1, ΔG2, and ΔGm is optimized. Further, in the passenger car tire, the gauge G1 is preferably in the range of G1 ≦ 8.0 [mm], and more preferably in the range of G1 ≦ 6.0 [mm]. Further, the gauge G2 is preferably in the range of 1.0 [mm] ≦ G2, and more preferably in the range of 2.0 [mm] ≦ G2. As a result, the rubber volume of the rim fitting portion inside the bead core 11 in the radial direction is optimized.

Further, the width Wc2 [mm] (see FIG. 4) of the innermost layer of the wire arrangement structure of the bead core 11, the rate of change ΔGm [%] at the midpoint Cm, and the tire inner diameter RD [inch] (see FIG. 2) are determined. It is preferable to have a relationship of 1.0 [% · mm / inch] ≦ Wc2 × ΔGm / RD ≦ 50 [% · mm / inch], and 2.0 [% · mm / inch] ≦ Wc2 × ΔGm / RD ≦ It is more preferable to have a relationship of 40 [% · mm / inch], and it is more preferable to have a relationship of 5.0 [% · mm / inch] ≦ Wc2 × ΔGm / RD ≦ 30 [% · mm / inch]. .. As a result, the relationship between the width Wc2 of the innermost layer of the bead core 11 and the rate of change ΔGm is optimized. That is, the above lower limit ensures the rim fitability of the tire. Further, the above upper limit improves the workability of tire rim assembly.

The width Wc2 of the innermost layer of the wire arrangement structure is measured as the maximum width including the innermost and outermost wire cross sections in the tire width direction as shown in FIG.

Further, the width Wc2 of the innermost layer of the wire arrangement structure is preferably in the range of 3.0 [mm] ≤ Wc2 ≤ 10.0 [mm], and 4.5 [mm] ≤ Wc2 ≤ 9.6 [mm]. ] Is more preferable.

[Bead core wire arrangement structure]
As shown in FIG. 6, the bead core 11 is formed by winding the bead wire 111 in an annular shape and in multiple directions, and has a predetermined wire arrangement structure in a cross-sectional view in the tire meridian direction. The wire arrangement structure is defined by the arrangement of the wire cross sections of the bead wires 111. Further, the wire arrangement structure is composed of a plurality of layers laminated in the tire radial direction, and these layers are composed of a plurality of wire cross sections arranged in a row in the tire width direction. Further, the innermost layer of the wire arrangement structure is substantially parallel to the rim fitting surface of the bead portion and faces the bead sheet 101 of the rim 10 when the tire rim is fitted (see FIG. 5).

In the manufacturing process of the bead core 11, a core forming jig (not shown) is used, and one or a plurality of bead wires 111 are wound around the core forming jig in a predetermined wire arrangement structure to form an unvulcanized bead core 11. It is molded. Then, the molded bead core 11 is pre-vulcanized before the vulcanization molding step of the green tire. Not limited to this, pre-vulcanization of the bead core 11 may be omitted, the unvulcanized bead core 11 may be incorporated into the green tire, and the vulcanization molding step of the green tire may be performed.

Further, the bead wire 111 is composed of a wire and an insulation rubber covering the wire (not shown). Also, the strands are made of steel. Further, it is preferable that the insulation rubber is made of a rubber composition having a Mooney viscosity of 70 [M] or more. Mooney viscosity is calculated according to JIS K6300-1: 2013.

Here, in the configuration of FIG. 2, as described above, the rewinding portion 132 of the carcass layer 13 comes into contact with the main body portion 131 of the carcass layer 13 to form a closed region X surrounding the bead core 11. Further, the rubber occupancy rate in the closed region X is set to be small, and the weight of the bead portion is reduced. At this time, in order to increase the durability of the bead portion, it is preferable to suppress the generation of the cavity portion in the closed region X.

Therefore, as shown in FIG. 6, the wire arrangement structure of the bead core 11 has a wedge shape that is convex toward the outer side in the tire radial direction. Specifically, the layer in which the number of arrangements of the wire cross section in the wire arrangement structure is the maximum (in FIG. 6, the second layer from the innermost layer) is defined as the maximum arrangement layer. At this time, the number of layers of the wire cross section outside the maximum array layer in the tire radial direction (three layers in FIG. 6) is the number of layers of the wire cross section inside the maximum array layer in the tire radial direction (in FIG. 6). More than 1 layer). Further, the number of arrangements of the wire cross sections in each layer on the outer side in the tire radial direction from the maximum arrangement layer monotonically decreases from the maximum arrangement layer toward the outer side in the tire radial direction. Further, it is preferable that the number of layers in the cross section of the wire is in the range of 4 or more and 6 or less. Further, it is preferable that the number of arrangements of the wire cross sections in the maximum arrangement layer of the wire arrangement structure is 4 or 5, and the number of arrangements of the wire cross sections of the outermost layer in the tire radial direction is 1 or 2.

Further, it is preferable that the wire cross sections are arranged in a close-packed structure in a region outside the tire radial direction from the maximum arrangement layer. The close-packed structure means a state in which the centers of three adjacent wire cross sections are arranged so as to form an equilateral triangle in a cross-sectional view in the tire meridian direction. In such a close-packed structure, the arrangement density of the wire cross section of the bead core 11 is increased and the core collapse resistance of the bead core 11 is improved as compared with the lattice arrangement structure in which the rows of wire cross sections are orthogonal to each other in the vertical and horizontal directions. In the close-packed state, it is not necessary for all the sets of adjacent wire cross sections to come into contact with each other, and some sets may be arranged with a slight gap (not shown).

In such a configuration, as shown in FIG. 5, the main body portion 131 and the rewinding portion 132 of the carcass layer 13 abut on the left and right side surfaces in the tire width direction of the bead core 11 and along the wedge shape of the wire arrangement structure in the tire radial direction. It extends outwards, merges in a Y shape, and comes into contact with each other. As a result, the gap between the confluence of the main body 131 and the rewinding portion 132 of the carcass layer 13 and the top portion (so-called bead top) on the outer side in the tire radial direction of the bead core 11 is reduced, and the durability of the bead portion is improved. In particular, it is preferable that the structure omitting the bead filler described above can reduce the rubber occupancy of the closed region X. Further, since the rewinding portion 132 of the carcass layer 13 bends and contacts the main body portion 131 at an obtuse angle, the bending amount of the rewinding portion 132 is small. As a result, the deformation of the carcass ply in the tire vulcanization molding step is suppressed, the stress acting on the bead core 11 is reduced, and the core collapse of the bead core 11 is appropriately suppressed.

Further, it is preferable that the number of arrangements of the wire cross sections in the innermost layer of the wire arrangement structure in the tire radial direction is 3 or 4, and the number of arrangements is the same as or smaller than the number of arrangements of the wire cross sections of the maximum arrangement layer.

Further, as shown in FIG. 6, the arrangement angles θ1 and θ2 of the wire cross sections at the corners inside the tire radial direction and inside and outside the tire width direction of the wire arrangement structure are defined, respectively. At this time, the arrangement angles θ1 and θ2 are in the range of 80 [deg] ≤ θ1 and 80 [deg] ≤ θ2. That is, the arrangement angles θ1 and θ2 of the wire cross section are substantially right angles or obtuse angles. Further, as shown in FIG. 6, it is preferable that the arrangement angles θ1 and θ2 of the wire cross section are in the range of 100 [deg] ≦ θ1 ≦ 150 [deg] and 100 [deg] ≦ θ2 ≦ 150 [deg]. In such a configuration, the arrangement angle θ2 of the wire cross section becomes substantially a right angle or more, the disorder of the wire arrangement structure at the time of tire vulcanization is suppressed, and the core collapse of the bead core 11 is effectively suppressed. Further, when the arrangement angles θ1 and θ2 of the wire cross section are obtuse angles, the carcass ply can be rewound along the inner corner portion of the bead core 11 in the tire radial direction, so that the rubber occupancy rate in the closed region X is reduced. The bead part can be made lighter.

The arrangement angles θ1 and θ2 are measured as angles formed by lines connecting the centers of the three wire cross sections constituting the corners of the wire arrangement structure.

Further, in FIG. 6, the maximum width Wc1 and the maximum height Hc1 of the bead core 11 and the total cross-sectional area S of the bead wire 111 in the bead core 11 have a relationship of 1.20 ≦ Wc1 × Hc1 / S ≦ 5.00. It is more preferable to have a relationship of 1.50 ≦ Wc1 × Hc1 / S ≦ 4.50, and more preferably to have a relationship of 1.80 ≦ Wc1 × Hc1 / S ≦ 4.00. As a result, the wire arrangement structure of the bead core 11 is optimized. That is, by the above lower limit, the number of arrangements of the wire cross sections is secured, and the rim fitability of the tire is ensured. Further, due to the above upper limit, the weight of the bead core 11 is reduced.

The total cross-sectional area S of the bead wire does not include the cross-sectional area of the insulation rubber.

Further, the total cross-sectional area S of the bead wire 111 is preferably in the range of 5 [mm ² ] ≦ S ≦ 35 [mm ² ], and is preferably in the range of 6 [mm ² ] ≦ S ≦ 32 [mm ² ]. Is more preferable, and it is further preferable that it is in the range of 7 [mm ² ] ≦ S ≦ 28 [mm ² ]. As a result, the total cross-sectional area S of the bead wire 111 is optimized. That is, by the above lower limit, the total cross-sectional area S of the bead wire 111 is secured, and the rim fitability of the tire is ensured. Further, due to the above upper limit, the weight of the bead core 11 is reduced.

Further, the outer diameter φ (see FIG. 6) of the bead wire 111 is preferably in the range of 0.8 [mm] ≤ φ ≤ 1.5 [mm], and 0.9 [mm] ≤ φ ≤ 1.4. It is more preferably in the range of [mm], and even more preferably in the range of 1.0 [mm] ≤ φ ≤ 1.3 [mm]. As a result, the outer diameter φ of the bead wire 111 is optimized. That is, by the above lower limit, the outer diameter φ of the bead wire 111 is secured, and the rim fitability of the tire is ensured. Further, due to the above upper limit, the weight of the bead core 11 is reduced.

Further, in FIG. 6, the height Hc2 from the tangent line L1 of the innermost layer of the wire arrangement structure to the maximum width position of the bead core 11 and the maximum height Hc1 of the bead core 11 are 1.10 ≦ (Hc1-Hc2) / Hc2. It is preferable to have a relationship of ≦ 2.80, and it is preferable to have a relationship of 1.30 ≦ (Hc1-Hc2) /Hc2 ≦ 2.50, and it is preferable to have a relationship of 1.50 ≦ (Hc1-Hc2) /Hc2 ≦ 2.30. It is more preferable to have the relationship of. As a result, the wire arrangement structure of the bead core 11 is optimized.

The maximum height Hc1 of the bead core is measured as the maximum height of the bead core with respect to the tangent line L1.

The height Hc2 at the maximum width position of the bead core is measured as the distance between the tangent line L1 and the virtual line connecting the center of the wire cross section constituting the maximum array layer. Further, in the configuration in which the wire arrangement structure includes a plurality of maximum arrangement layers, the maximum arrangement layer on the outermost side in the tire radial direction is used, and the height Hc2 at the maximum width position is measured.

For example, in the configuration of FIG. 6, the number of layers of the wire cross section is 5, and the number of arrangements of the wire cross sections is set to 3-4--3-2-1 in order from the innermost layer in the tire radial direction. Therefore, the number of arrangements of the wire cross sections in the maximum arrangement layer is 4. Further, the number of layers of the wire cross section outside the maximum array layer in the tire radial direction is 3, and the number of layers of the wire cross section inside the maximum array layer in the tire radial direction is 1. Therefore, the maximum array layer is asymmetric in the tire radial direction, and is arranged so as to be biased inward in the tire radial direction from the center position in the tire radial direction of the wire arrangement structure. again,
The wire arrangement structure has a long structure outside the tire radial direction from the maximum arrangement layer. Further, the number of arrangements of the wire cross sections in each layer decreases by one from the maximum arrangement layer toward the outer side in the tire radial direction. Also, all wire cross sections are arranged in a close-packed structure. Therefore, the arrangement angles θ1 and θ2 of the wire cross sections at the left and right corners of the wire arrangement structure in the tire radial direction are both about 135 [deg] (specifically, in the range of 130 [deg] to 140 [deg]). Is. Further, the maximum array layer of the wire cross section is not the innermost layer in the tire radial direction. Further, the number of arrangements of the wire cross sections in each layer is increased by one from the innermost layer to the largest arrangement layer. This optimizes the wire arrangement structure.

Further, in FIG. 5, the tire radial distance Hg from the tire radial outer end portion of the bead core 11 to the contact portion between the main body portion 131 of the carcass layer 13 and the rewinding portion 132 is the outer diameter φ of the bead wire 111. Therefore, it is preferable to have a relationship of Hg / φ≤7.0, and more preferably to have a relationship of Hg / φ≤3.0. This improves the rigidity around the bead core 11. The lower limit of the ratio Hg / φ is 0 ≦ Hg / φ when Hg = 0.

[Gauge of rim fitting part]
FIG. 8 is an explanatory view showing the rim fitting portion shown in FIG. The figure shows the rim fitting portion in the state before rim assembly. In the figure, the same components as those shown in FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 8, as described above, the gauge G2 in the tire radial direction from the contact point C2 between the tangent line L1 of the innermost layer of the wire arrangement structure and the outermost wire cross section in the tire width direction to the rim fitting surface is defined. At this time, it is preferable that the gauge G2 and the outer diameter φ of the bead wire 111 (see FIG. 6) have a relationship of 1.3 ≦ G2 / φ ≦ 9.5, and 1.8 ≦ G2 / φ ≦ 5.5. It is more preferable to have the relationship of. As a result, the gauge G2 of the rim fitting portion is optimized. That is, by the above lower limit, the gauge G2 of the rim fitting portion is secured, and the rim fitting property of the tire is secured. Further, by the above upper limit, deterioration of tire rim assembly workability due to an excessive gauge G2 of the rim fitting portion is suppressed.

Further, in FIG. 8, an intersection Q of a straight line passing through the contact point C2 of the bead core 11 and parallel to the tire width direction and the outer wall surface of the rim fitting portion in the tire width direction is defined. Further, a gauge Wh in the tire width direction from the contact C2 of the bead core 11 to the point Q of the rim fitting surface is defined. At this time, it is preferable that the gauge Wh and the outer diameter φ (see FIG. 6) of the bead wire 111 have a relationship of 2.0 ≦ Wh / φ ≦ 15.0, and 2.5 ≦ Wh / φ ≦ 10.0. It is more preferable to have the relationship of. As a result, the gauge Wh of the rim fitting portion is optimized. That is, by the above lower limit, the gauge Wh of the rim fitting portion is secured, the rim fitting property of the tire is secured, and the durability of the rim fitting portion is secured. Further, by the above upper limit, deterioration of tire rim assembly workability due to an excessive gauge Wh of the rim fitting portion is suppressed.

Further, as shown in FIG. 8, the cushion rubber layer 20 is inserted between the innermost layer of the bead core 11 and the rim cushion rubber 17. The cushion rubber layer 20 is a member having a rubber hardness lower than that of the rim cushion rubber 17, and includes, for example, an inner liner 18, a tie rubber (not shown) for adhering the inner liner 18 and the carcass layer 13, and the carcass ply. Does not include. Further, the cushion rubber layer 20 may have an integral structure with respect to the inner liner 18 and the tie rubber, or may have a separate structure (not shown). Further, the cushion rubber layer 20 may be made of the same rubber material as the inner liner 18 and the tie rubber described above, or may be made of a different rubber material (not shown). Further, it is preferable that the cushion rubber layer 20 crosses the range from the contact C1 to the midpoint Cm of the bead core 11, preferably the range from the contact C1 to the contact C2 in the tire width direction. In such a configuration, the cushion rubber layer 20 is interposed between the innermost layer of the bead core 11 and the rim fitting surface of the bead portion, so that the rate of change ΔG1, ΔG2, ΔGm of the rim fitting portion is increased, and the tire rim is fitted. Improves compatibility. Further, the contact pressure of the rim fitting surface with respect to the rim 10 is made uniform.

Further, the rubber hardness of the cushion rubber layer 20 is preferably 5 or more lower than the rubber hardness of the rim cushion rubber 17, and more preferably 8 or more. As a result, the action of increasing the rate of change ΔG1, ΔG2, and ΔGm of the rim fitting portion can be appropriately obtained.

For example, in the configuration of FIG. 8, in the cross-sectional view in the tire meridian direction, the cushion rubber layer 20 extends from the tire inner cavity surface to the outside in the tire width direction along the rewinding portion 132 of the carcass layer 13, and the bead core 11 It is interposed between the rim cushion rubber 17 and the rim cushion rubber 17. Further, the cushion rubber layer 20 extends beyond the midpoint Cm of the innermost layer of the bead core 11 to the outermost contact C2. Further, the end portion of the cushion rubber layer 20 on the outer side in the tire width direction is terminated on the inner side in the tire radial direction with respect to the tangent line L1 of the bead core 11. Therefore, the end portion of the cushion rubber layer 20 does not extend to the outer side surface of the bead core 11 in the tire width direction. This effectively enhances the rate of change ΔG1, ΔG2, ΔGm between the bead core 11 and the rim fitting surface (particularly the bead base Bb), while the flange 102 of the bead core 11 and the rim 10 (see FIG. 2). ) Is properly secured. However, the present invention is not limited to this, and the end portion of the cushion rubber layer 20 on the outer side in the tire width direction may extend to the outer side in the tire radial direction from the tangent line L1 of the bead core 11.

Further, in FIG. 8, it is preferable that the thicknesses Tc1 and Tc2 of the cushion rubber layer 20 between the measurement points C1, P1; C2 and P2 of the gauges G1 and G2 of the rim fitting portion have a relationship of Tc2 <Tc1. That is, it is preferable that the thickness Tc1 of the cushion rubber layer 20 on the bead to Bt side is thicker than the thickness Tc2 of the cushion rubber layer 20 on the bead heel Bh side. As a result, the rate of change ΔG1 of the rim fitting portion on the bead to Bt side becomes larger than the rate of change ΔG2 of the rim fitting portion on the bead heel Bh side (ΔG2 <ΔG1), and the rim fitting property of the tire is improved. improves.

Further, as described above, by adjusting the relationship of the thickness of the cushion rubber layer 20 between the measurement points C1, P1; C2, P2; Cm and Pm of the gauges G1, G2 and Gm of the rim fitting portion, the rim The relationship between the rate of change of the fitting portion ΔG1, ΔG2, and ΔGm can be adjusted.

Further, it is preferable that the average value of the thickness of the cushion rubber layer 20 in the region from the contact C1 to the contact C2 in the tire width direction is in the range of 0.3 [mm] or more and 3.0 [mm] or less. As a result, the average thickness of the cushion rubber layer 20 is optimized. That is, according to the above lower limit, the action of the cushion rubber layer 20 that increases the rate of change ΔG1, ΔG2, and ΔGm of the rim fitting portion can be appropriately obtained. Further, by the above upper limit, the decrease in the rigidity of the rim fitting portion due to the excessive cushion rubber layer 20 is suppressed.

Further, in FIG. 8, it is preferable that the gauge G1 of the rim fitting portion on the bead to Bt side and the thickness Tc1 of the cushion rubber layer 20 have a relationship of 0.03 ≦ Tc1 / G1 ≦ 0.95. It is more preferable to have a relationship of 0.05 ≦ Tc1 / G1 ≦ 0.85. As a result, the average thickness of the cushion rubber layer 20 is optimized. That is, by the above lower limit, the action of the cushion rubber layer 20 is properly secured, and the rate of change ΔG1 of the rim fitting portion increases. Further, by the above upper limit, the gauge G1 of the rim cushion rubber 17 is secured, and the rim fitability of the tire is properly ensured.

Further, on the tire cavity side, the cushion rubber layer 20 is preferably 5 [mm] from the measurement point on the tire radial outer side of the height H1 of the bead core 11 (see FIG. 2) toward the tire radial outer side. It is preferable to extend the above.

[Shape of rim fitting surface]
FIG. 9 is an explanatory view showing the rim fitting portion shown in FIG. The figure shows the rim fitting portion in the state before rim assembly. In the figure, the same components as those shown in FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 9, the tangent line of the rim fitting surface at the intersection P2 is defined as the extension line L2 of the bead base Bb in the cross-sectional view in the tire meridian direction in the state before the rim assembly.

At this time, the inclination angle α of the extension line L2 of the bead base Bb with respect to the tangent line L1 of the bead core 11 is preferably in the range of 3 [deg] ≦ α ≦ 15 [deg], and 6 [deg] ≦ α ≦ 12. It is more preferable that it is in the range of [deg].

Further, the inclination angle α [deg] of the extension line L2 of the bead base Bb, the rate of change ΔGm [%] of the rim fitting portion, and the tire nominal width WA [dimensionless] are 0 [% · deg] ≦. It is preferable to have a relationship of ΔGm × α / WA ≦ 7 [% · deg], and it is more preferable to have a relationship of 0.5 [% · deg] ≦ ΔGm × α / WA ≦ 5.0 [% · deg]. preferable. As a result, the ratio ΔGm × α / WA, which indicates the rim fitability of the tire, is optimized. That is, in general, the larger the tire nominal width WA, the lower the tire rim fitability tends to be. Further, as the inclination angle α of the bead base Bb and the rate of change ΔGm of the rim fitting portion are larger, the fitting pressure with respect to the rim is increased, and the rim fitting property of the tire is improved. Therefore, due to the above lower limit, the ratio ΔGm × α / WA becomes large, and the rim fitability of the tire is improved. Further, the above upper limit suppresses deterioration of tire rim assembly workability due to excessive fitting pressure on the rim. When the inclination angle α = 0 [deg], ΔGm × α / WA = 0.

Further, as shown in FIG. 9, in a cross-sectional view in the tire meridional direction, the bead base Bb has a shape (so-called two-step tapered shape) in which two types of straight portions having different inclination angles are connected to each other. In this case, an extension line L2 of a straight portion on the bead heel Bh side of the bead base Bb of the rim fitting surface and an extension line L3 of the straight portion on the bead to Bt side are defined.

At this time, it is preferable that the inclination angles α and β of the extension lines L2 and L3 of the bead base Bb with respect to the tangent line L1 of the bead core 11 have a relationship of 0 ≦ β / α ≦ 5.0, and 1.8 ≦ β /. It is more preferable to have a relationship of α ≦ 4.0. As a result, the two-step taper shape of the bead base Bb is optimized. That is, according to the above lower limit, the effect of improving the rim fitability of the tire due to the two-step taper shape can be appropriately obtained. Further, by the above upper limit, the occurrence of vulcanization failure in the bead base Bb is suppressed.

Further, in FIG. 9, the intersection R of the above two types of straight lines of the bead base Bb is defined.

At this time, the distance Lr in the tire width direction from the bead to Bt to the intersection R and the distance Lm in the tire width direction from the bead to Bt to the midpoint Cm are 0.50 ≦ Lr / Lm ≦ 4.0. It is preferable to have the relationship of 0.70 ≦ Lr / Lm ≦ 3.3, and it is more preferable to have the relationship of 0.70 ≦ Lr / Lm ≦ 3.3. As a result, the position of the intersection R is optimized, and the effect of improving the rim fitability of the tire due to the two-step taper shape can be appropriately obtained.

For example, in the configuration of FIG. 9, the arrangement angle θ1 (see FIG. 6) of the wire cross section at the corner portion of the wire arrangement structure of the bead core 11 inside the tire radial direction and inside the tire width direction is 130 [deg] or more and 140 [. deg] It is in the following range. Further, the above-mentioned two types of straight lines of the bead base Bb are connected by a smooth arc that is convex outward in the tire radial direction. Further, the intersection point R is located between the contact point C1 of the bead core 11 and the midpoint Cm.

Further, in FIG. 9, the distance Dt in the tire radial direction and the distance Wt in the tire width direction from the contact point C1 of the bead core 11 to the bead to Bt are defined, respectively. At this time, the relationship between the distances Dt and Wt and the gauge G1 in the tire radial direction from the contact point C1 to the rim fitting surface is 7 [deg] ≤ arctan {(Dt-G1) / Wt} ≤ 30 [deg]. It is preferable to have, and it is more preferable to have a relationship of 9 [deg] ≤ arctan {(Dt-G1) / Wt} ≤ 25 [deg]. As a result, the slope of the rim fitting surface with respect to the tire axial direction from the bead core 11 to the bead to Bt is optimized. That is, by the above lower limit, the gradient of the rim fitting surface is secured, and the rim fitting property of the tire is ensured. Further, the upper limit suppresses a decrease in tire rim assembly workability due to an excessive gradient of the rim fitting surface.

The distances Dt and Wt from the contact point C1 to the bead to Bt are measured in the state before the tire rim is assembled.

[Modification example]
10 to 14 are explanatory views showing a modified example of the bead core shown in FIG. These figures show a radial cross-sectional view of the unvulcanized bead core 11 at the time of a single component.

In the configuration of FIG. 6, the tangent line L1 with respect to the innermost layer of the bead core 11 is parallel to the tire width direction. Therefore, the inclination angle X of the tangent line L1 with respect to the tire width direction is X = 0 [deg].

However, the present invention is not limited to this, and as shown in FIG. 10, the bead core 11 may be inclined with respect to the tire width direction. Specifically, the bead core 11 may be inclined inward in the tire radial direction on the bead to Bt (see FIG. 5) side. In such a configuration, the tangent line L1 of the innermost layer of the bead core 11 approaches parallel to the bead base Bb of the rim fitting surface. At this time, it is preferable that the inclination angle X of the tangent line L1 with respect to the tire width direction is in the range of −10 [deg] ≦ X ≦ 30 [deg]. The range of the relative inclination angle α of the extension line L2 of the bead base Bb with respect to the tangent line L1 of the bead core 11 is as described above.

Further, in the configuration of FIG. 6, as described above, the number of arrangements of the wire cross sections is set to 3-4--3-2-1 in order from the innermost layer in the tire radial direction. Therefore, the number of layers of the wire cross section is 5, and the number of arrangements of the wire cross sections of the outermost layer in the tire radial direction is 1.

On the other hand, in the configuration of FIG. 11, the number of layers of the wire cross section is 4, and the number of arrangements of the wire cross sections is set to 3-4-3-2 in order from the innermost layer in the tire radial direction. Further, in the configuration of FIG. 12, the number of layers of the wire cross section is 6, and the number of arrangements of the wire cross sections is set to 3-4-5-4-3-2 in order from the innermost layer in the tire radial direction. As described above, the number of layers in the cross section of the wire may be 4 or 6. Further, the number of arrangements of the wire cross sections of the outermost layer in the tire radial direction may be two. Even in such a case, the number of layers of the wire cross section outside the tire radial direction from the maximum array layer (2 layers in FIG. 11 and 3 layers in FIG. 12) is the wire cross section inside the tire radial direction from the maximum array layer. It is larger than the number of layers (1 layer in FIG. 11 and 2 layers in FIG. 12). Further, the number of arrangements of the wire cross sections in each layer decreases by one from the maximum arrangement layer toward the outer side in the tire radial direction.

Further, in the configuration of FIG. 6, the number of wire cross-section arrangements in the innermost layer in the tire radial direction is smaller than the number of wire cross-section arrangements in the maximum arrangement layer (second layer from the innermost layer). Further, all the wire cross sections constituting the wire arrangement structure are arranged by the close-packed structure. Therefore, the arrangement angles θ1 and θ2 of the wire cross sections at the corners inside the tire radial direction and inside and outside the tire width direction of the wire arrangement structure are both in the range of 130 [deg] or more and 140 [deg] or less.

On the other hand, in the configurations of FIGS. 13 and 14, the number of layers of the wire cross section is 5, and the number of arrangements of the wire cross sections is set to 4-4--3-2-1 in order from the innermost layer in the tire radial direction. ing. Therefore, the number of wire cross-section arrangements in the innermost layer is the same as the number of wire cross-section arrangements in the maximum arrangement layer. Further, in the configuration of FIG. 13, the arrangement angle θ1 of the wire cross section at the corner portion inside the tire radial direction and inside the tire width direction of the wire arrangement structure is an acute angle, and is in the range of 55 [deg] or more and 65 [deg] or less. be. On the other hand, the arrangement angle θ2 of the wire cross section at the outer corner in the tire width direction is an obtuse angle, and is in the range of 130 [deg] or more and 140 [deg] or less. Further, in the configuration of FIG. 14, the arrangement angles θ1 and θ2 of the wire cross sections at the left and right corners inside the tire radial direction of the wire arrangement structure are both substantially right angles, and are 85 [deg] or more and 95 [deg] or less. It is in the range. As described above, it is preferable that at least the arrangement angle θ2 of the wire cross section at the outer corner portion in the tire width direction is about a right angle or an obtuse angle. Further, in the configuration of FIG. 14, the wire cross sections are arranged in a grid pattern on the inner side in the tire radial direction from the maximum array layer. As described above, the wire cross sections may be arranged by the close-packing structure at least in each layer on the outer side in the tire radial direction from the maximum arrangement layer.

[Gauge on the side of the tire]
FIG. 15 is an enlarged view showing a tire side portion of the pneumatic tire shown in FIG. The figure shows an enlarged cross-sectional view in the tire meridian direction at the tire maximum width position A.

In FIG. 15, the total thickness K1 of the tire side portion at the tire maximum width position A is preferably in the range of 2.5 [mm] ≤ K1 ≤ 6.5 [mm], preferably 3.0 [mm] ≤. It is more preferable that the range is K1 ≦ 6.0 [mm]. As a result, the total thickness K1 of the tire side portion is optimized. That is, by the above lower limit, the total thickness K1 of the tire side portion is secured, and the rolling resistance of the tire is secured. Further, the weight reduction of the tire is ensured by the above upper limit.

The total thickness K1 of the tire side portion is measured as the distance between the tire outer surface and the tire outer surface at the tire maximum width position A in the cross-sectional view in the tire meridional direction.

Further, the thickness K2 of the sidewall rubber 16 at the tire maximum width position A is preferably in the range of 0.3 [mm] ≤ K2 ≤ 3.0 [mm], and 0.5 [mm] ≤ K2 ≤. It is more preferably in the range of 2.5 [mm]. As a result, the thickness K2 of the sidewall rubber 16 is optimized. That is, by the above lower limit, the thickness K2 of the sidewall rubber 16 is secured, and the cut resistance of the tire side portion is ensured. Further, the weight reduction of the tire is ensured by the above upper limit.

[effect]
As described above, the pneumatic tire 1 is composed of a bead core 11 formed by winding one or a plurality of bead wires in an annular shape and a plurality of layers, and a single-layer or a plurality of layers of car cushion ply, and wraps the bead core 11. A carcass layer 13 that is rewound and bridged over the bead core 11 and a rim cushion rubber 17 that is arranged along the rewinding portion of the carcass layer 13 and forms a rim fitting surface of the bead portion are provided (see FIG. 1). The rewinding portion 132 of the carcass layer 13 contacts the main body portion 131 of the carcass layer 13 to form a closed region X surrounding the bead core 11 (see FIG. 2). Further, in the cross-sectional view in the tire meridian direction, the rubber occupancy rate in the closed region X is in the range of 15 [%] or less. Further, the heat shrinkage of the carcass cord 130 (see FIG. 3) constituting the carcass ply is in the range of 0.1 [%] or more and 1.5 [%] or less.

In such a configuration, (1) the rubber occupancy rate in the closed region X surrounded by the main body portion 131 and the rewinding portion 132 of the carcass layer 13, that is, the rubber volume around the bead core 11 is set to be very low. As a result, the bead filler can be omitted, which has the advantage of reducing the weight of the tire. Further, (2) there is an advantage that the heat shrinkage rate of the carcass cord 130 is optimized. That is, since the heat shrinkage rate of the carcass cord 130 is set low by the above upper limit, the deformation of the carcass ply due to the vulcanization heat is suppressed in the tire vulcanization molding step, and the stress acting on the bead core 11 is reduced. Sulfur. As a result, the core collapse of the bead core 11 is appropriately suppressed, and the rim fitability of the tire is improved. Further, by the above lower limit, the fibrilization of the carcass code 130 is suppressed, and the durability of the carcass ply is ensured.

Further, in the pneumatic tire 1, the carcass cord 130 (see FIG. 3) is a composite yarn made of aramid fiber and polyester fiber. In such a configuration, the amount of yarn can be reduced as compared with, for example, a carcass cord made of only polyester fibers (not shown), so that the cord diameter of the carcass cord 130 can be reduced. This has the advantage that the gauge of the carcass ply can be thinned while reducing the heat shrinkage rate of the carcass cord 130. Further, for example, as compared with a carcass cord (not shown) composed of only aramid fibers, there is an advantage that the fibrilization of the carcass cord 130 is suppressed and the durability of the carcass ply is ensured.

Further, in the pneumatic tire 1, the carcass cord 130 is configured by top-twisting a plurality of aramid lower twist yarns 1301 made of aramid fiber bundles and at least one polyester lower twist yarn 1302 made of polyester fiber bundles. It is a composite yarn Y (see FIG. 3). In such a configuration, since the total strength of the carcass cord 130 can be increased and the amount of yarn of the carcass cord 130 can be reduced, there is an advantage that the carcass ply can be thinned while increasing the pressure resistance of the carcass ply.

Further, in the pneumatic tire 1, the total fineness of the aramid lower twisted yarn 1301 is in the range of 400 [dtex] or more and 1200 [dtex] or less, and the total fineness of the polyester lower twisted yarn 1302 is 500 [dtex] or more and 1200 [dtex] or less. ], And the total fineness D of the composite yarn Y is in the range of 1000 [dtex] or more and 2400 [dtex] or less. This has the advantage that the total fineness of each lower twisted yarn constituting the carcass cord 130 and the total fineness D of the composite yarn are optimized. That is, the strength of the carcass cord 130 is ensured by the above lower limit, and the weight reduction of the carcass ply is ensured by the above upper limit.

Further, in the pneumatic tire 1, the twist coefficient K of the composite yarn Y is in the range of 2000 or more and 2400 or less. This has the advantage that the twist coefficient K of the composite yarn Y constituting the carcass cord 130 is optimized. That is, the strength of the carcass cord 130 is ensured by the above lower limit, and the weight reduction of the carcass ply is ensured by the above upper limit.

Further, in the pneumatic tire 1, the cord diameter of the carcass cord 130 is in the range of 0.30 [mm] or more and 0.55 [mm] or less. As a result, the function of the carcass cord 130 is ensured, and there is an advantage that the carcass ply is thinned and has a pressure resistance.

Further, in the pneumatic tire 1, the intermediate elongation of the carcass cord 130 is in the range of 1.0 [%] or more and 10 [%] or less. As a result, the function of the carcass cord 130 is ensured, and there is an advantage that the carcass ply is thinned and has a pressure resistance.

Further, in the pneumatic tire 1, the number of ends of the carcass cord 130 is in the range of 35 [lines / 50 mm] or more and 85 [lines / 50 mm] or less. As a result, the function of the carcass cord 130 is ensured, and there is an advantage that the carcass ply is thinned and has a pressure resistance.

Further, in the pneumatic tire 1, the end portion of the winding portion 132 of the carcass layer 13 is inside the tire maximum width position in the tire radial direction (see FIG. 2). In the so-called low turn-up structure in which the winding height of the carcass layer 13 is low, the deformation of the carcass ply in the tire vulcanization molding step becomes large, and the core collapse of the bead core 11 tends to occur easily. Therefore, by adopting the above configuration in such a low turn-up structure, there is an advantage that the effect of suppressing the core collapse of the bead core 11 can be remarkably obtained.

Further, in the pneumatic tire 1, the radial height H2 of the contact portion between the main body portion 131 and the rewinding portion 132 of the carcass layer 13 is 0.80 ≦ H2 / with respect to the radial height H1 of the bead core 11. It has a relationship of H1 ≦ 3.00 (see FIG. 2). This has the advantage that the radial height H2 of the self-contact portion of the carcass layer 13 is optimized. That is, by the above lower limit, the rewinding portion 132 stably contacts the main body portion 131, and the deformation of the carcass ply in the tire vulcanization molding step is suppressed. As a result, the stress acting on the bead core 11 is reduced, and the core collapse of the bead core 11 is appropriately suppressed. Further, the upper limit suppresses an increase in tire weight due to an excessive rewinding portion 132.

Further, in the pneumatic tire 1, the bead core 11 has a predetermined wire arrangement structure in which the wire cross sections of the bead wires 111 are arranged in a cross-sectional view in the tire meridional direction (see FIG. 6). Further, the layer having the maximum number of arrangements of the wire cross sections in the wire arrangement structure (in FIG. 6, the second layer from the innermost layer) is defined as the maximum arrangement layer. At this time, the number of layers of the wire cross section outside the maximum array layer in the tire radial direction (three layers in FIG. 6) is the number of layers of the wire cross section inside the maximum array layer in the tire radial direction (in FIG. 6). More than one of the innermost layers). Further, the number of arrangements of the wire cross sections in each layer on the outer side in the tire radial direction from the maximum arrangement layer monotonically decreases from the maximum arrangement layer toward the outer side in the tire radial direction (see FIG. 6). In such a configuration, the rewinding portion 132 of the carcass layer 13 bends and contacts the main body portion 131 at an obtuse angle, so that the bending amount of the rewinding portion 132 is small. This has the advantage that the deformation of the carcass ply in the tire vulcanization molding step is suppressed, the stress acting on the bead core 11 is reduced, and the core collapse of the bead core 11 is appropriately suppressed.

Further, in the pneumatic tire 1, the bead core 11 has a predetermined wire arrangement structure in which the wire cross sections of the bead wires 111 are arranged in a cross-sectional view in the tire meridional direction (see FIG. 6). Further, the arrangement angle θ2 of the wire cross section at the corner portion of the wire arrangement structure inside the tire radial direction and outside the tire width direction is in the range of 80 [deg] ≦ θ2 (see FIG. 6). In such a configuration, the arrangement angle θ2 of the wire cross section becomes substantially a right angle or more, the disorder of the wire arrangement structure at the time of tire vulcanization is suppressed, and there is an advantage that the core collapse of the bead core 11 is effectively suppressed.

Further, in the pneumatic tire 1, the bead core 11 has a predetermined wire arrangement structure in which the wire cross sections of the bead wires 111 are arranged in a cross-sectional view in the tire meridional direction (see FIG. 6). Further, the arrangement angle θ2 of the wire cross section at the corner portion of the wire arrangement structure inside the tire radial direction and outside the tire width direction is in the range of 100 [deg] ≤ θ2 ≤ 150 [deg] (see FIG. 6). This has the advantage that the disorder of the wire arrangement structure during tire vulcanization is suppressed, and the core collapse of the bead core 11 is effectively suppressed.

Further, in the pneumatic tire 1, the actual length La2 of the contact portion between the main body portion 131 and the rewinding portion 132 of the carcass layer 13 is 0.30 ≦ La2 / La1 ≦ with respect to the peripheral length La1 of the closed region X. It has a relationship of 2.00. As a result, the actual length La2 of the self-contact portion of the carcass layer 13 is optimized. That is, the above lower limit has the advantage that the actual length La2 of the self-contact portion of the carcass layer 13 is secured, the deformation of the carcass ply in the tire vulcanization molding step is suppressed, and the core collapse of the bead core 11 is appropriately suppressed. be. Further, the upper limit suppresses an increase in tire weight due to an excessive rewinding portion 132.

Further, in the pneumatic tire 1, the bead core 11 has a predetermined wire arrangement structure in which the wire cross sections of the bead wires 111 are arranged in a cross-sectional view in the tire meridional direction (see FIG. 6). Further, the contact point C2 of the tangent line L1 which is in contact with the innermost layer in the tire radial direction and the innermost and outermost wire cross sections in the tire width direction from the rim fitting surface side in the wire arrangement structure and the tangent line L1 with respect to the outermost wire cross section. Is defined (see FIG. 5). Further, the gauge G2 in the tire radial direction from the contact C2 to the rim fitting surface and the outer diameter φ (see FIG. 6) of the bead wire 111 have a relationship of 1.3 ≦ G2 / φ ≦ 9.5. As a result, the gauge G2 of the rim fitting portion is optimized. That is, by the above lower limit, the gauge G2 of the rim fitting portion is secured, and the rim fitting property of the tire is secured. Further, by the above upper limit, deterioration of tire rim assembly workability due to an excessive gauge G2 of the rim fitting portion is suppressed.

FIG. 16 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment of the present invention. FIG. 17 is an explanatory diagram showing a bead core of a conventional test tire.

In this performance test, a plurality of types of test tires having a tire size of 205 / 55R16 were evaluated for (1) tire mass, (2) core collapse resistance, and (3) steering stability.

(1) The tire mass is calculated as an average value of the masses of five test tires having the same structure. Then, based on this measurement result, an index evaluation is performed using the conventional example as a reference (100). The smaller the value of this evaluation, the lighter the test tire, which is preferable. Further, if the index is 99 or less, it can be said that the weight of the tire is reduced as compared with the existing tire structure provided with the bead filler.

(2) In the evaluation of core collapse resistance, the entire circumference of the bead part of the tire after vulcanization is observed by a non-destructive test (for example, X-ray CT system), and the presence or absence of core collapse is confirmed, and there is no core collapse. If there is a core collapse, it is judged as "OK", and if there is a core collapse, it is judged as "NG". The number of observations was 20 for each example.

(3) In the evaluation of steering stability, the test vehicle runs on a test course on a dry road surface having a flat circuit at 60 [km / h] to 100 [km / h]. Then, the test driver performs a sensory evaluation on the steerability at the time of lane change and cornering and the stability at the time of going straight. This evaluation is performed by an exponential evaluation based on the conventional example (100), and the larger the value is, the more preferable.

The test tires of Examples 1 to 12 are provided with a structure (see FIGS. 1 and 2) in which the bead filler is omitted, so that the weight of the tire can be reduced. Further, the bead core 11 has the structure shown in FIGS. 2 and 6. Further, the carcass cord 130 of the carcass layer 13 is a composite yarn formed by top-twisting two aramid lower twisted yarns 1301 and 1301 made of an aramid fiber bundle and one polyester lower twisted yarn 1302 made of a polyester fiber bundle. It is composed of Y (see FIG. 3). Further, the tire cross-sectional height SH is 112 [mm], and the height H1 of the bead core 11 is 5.0 [mm].

In the conventional test tire, the bead core 11 has the wire arrangement structure shown in FIG. 17 in the configuration of the test tire of the first embodiment. In the test tire of the comparative example, the bead core 11 has the wire arrangement structure of FIG. 6 in the configurations of FIGS. 1 and 2.

As shown by the test results, it can be seen that in the test tires of Examples 1 to 12, the weight of the tire is reduced and the core collapse resistance of the bead core and the steering stability of the tire are improved.

1: Pneumatic tire, 11: Bead core, 111: Bead wire, 13: Carcass layer, 131: Main body, 132: Rewinding part, 130: Carcass cord, 1301: Aramid lower twist yarn, 1302: Polyester lower twist yarn, 14: Belt layer , 141, 142: Crossed belt, 143: Belt cover, 144: Belt edge cover, 15: Tread rubber, 16: Sidewall rubber, 17: Rim cushion rubber, 18: Inner liner, 19: Outer reinforcing rubber, 10: Rim , 101: bead sheet, 102: flange

Claims (15)

A bead core made by winding one or a plurality of bead wires in an annular shape and multiple times, and a carcass layer composed of a single layer or a plurality of layers of carcass ply and wound so as to wrap around the bead core and straddled over the bead core. A pneumatic tire provided with a rim cushion rubber arranged along the rewinding portion of the carcass layer and forming a rim fitting surface of the bead portion.
The rewinding portion of the carcass layer contacts the main body of the carcass layer to form a closed region surrounding the bead core.
In the cross-sectional view in the tire meridian direction, the rubber occupancy in the closed region is in the range of 15 [%] or less .
The heat shrinkage of the carcass cord constituting the carcass ply is in the range of 0.1 [%] or more and 1.5 [%] or less .
The rubber occupancy is calculated as the ratio of the cross-sectional area of the rubber material around the bead core in the closed area to the total cross-sectional area of the closed area, and
A pneumatic tire, wherein the heat shrinkage of the carcass cord is measured at a temperature of 150 ± 3 [° C.] according to a test method for dry heat shrinkage in JIS L1017 . The pneumatic tire according to claim 1, wherein the carcass cord is a composite yarn made of aramid fiber and polyester fiber. The invention according to claim 1 or 2, wherein the carcass cord is a composite yarn formed by top-twisting a plurality of aramid lower twist yarns made of an aramid fiber bundle and at least one polyester lower twist yarn made of a polyester fiber bundle. Pneumatic tires. The total fineness of the aramid lower twisted yarn is in the range of 400 [dtex] or more and 1200 [dtex] or less, and the total fineness of the polyester lower twisted yarn is in the range of 500 [dtex] or more and 1200 [dtex] or less. The pneumatic tire according to claim 3, wherein the total fineness D of the yarn is in the range of 1000 [dtex] or more and 2400 [dtex] or less. The pneumatic tire according to any one of claims 2 to 4, wherein the twist coefficient K of the composite yarn is in the range of 2000 or more and 2400 or less. The pneumatic tire according to any one of claims 1 to 5, wherein the diameter of the carcass cord is in the range of 0.30 [mm] or more and 0.55 [mm] or less. The pneumatic tire according to any one of claims 1 to 6, wherein the intermediate elongation of the carcass cord is in the range of 1.0 [%] or more and 10 [%] or less. The pneumatic tire according to any one of claims 1 to 7, wherein the number of ends of the carcass cord is in the range of 35 [lines / 50 mm] or more and 85 [lines / 50 mm] or less. The pneumatic tire according to any one of claims 1 to 8, wherein the end portion of the winding portion of the carcass layer is inside the tire maximum width position in the tire radial direction. The radial height H2 of the contact portion between the main body portion and the rewinding portion of the carcass layer has a relationship of 0.80 ≦ H2 / H1 ≦ 3.00 with respect to the radial height H1 of the bead core. The pneumatic tire according to any one of claims 1 to 8. The bead core has a predetermined wire arrangement structure formed by arranging the wire cross sections of the bead wires in a cross-sectional view in the tire meridian direction.
The layer in which the number of arrangements of the wire cross section in the wire arrangement structure is the maximum is defined as the maximum arrangement layer.
The number of layers of the wire cross section outside the maximum array layer in the tire radial direction is larger than the number of layers of the wire cross section inside the tire radial direction with respect to the maximum array layer, and
The air according to any one of claims 1 to 10, wherein the number of arrangements of the wire cross sections in each layer outside the tire radial direction from the maximum arrangement layer monotonically decreases from the maximum arrangement layer toward the tire radial outside. Tires with tires. The bead core has a predetermined wire arrangement structure formed by arranging the wire cross sections of the bead wires in a cross-sectional view in the tire meridian direction, and
The invention according to any one of claims 1 to 11, wherein the arrangement angle θ2 of the wire cross section at the corner portion inside the tire radial direction and outside the tire width direction of the wire arrangement structure is in the range of 80 [deg] ≦ θ2. Pneumatic tires. The bead core has a predetermined wire arrangement structure formed by arranging the wire cross sections of the bead wires in a cross-sectional view in the tire meridian direction, and
One of claims 1 to 12, wherein the arrangement angle θ2 of the wire cross section at the corner portion inside the tire radial direction and outside the tire width direction of the wire arrangement structure is in the range of 100 [deg] ≤ θ2 ≤ 150 [deg]. Pneumatic tires listed in one. The claim that the actual length La2 of the contact portion between the main body portion and the rewinding portion of the carcass layer has a relationship of 0.30 ≦ La2 / La1 ≦ 2.00 with respect to the peripheral length La1 of the closed region. The pneumatic tire according to any one of 1 to 13. The bead core has a predetermined wire arrangement structure formed by arranging the wire cross sections of the bead wires in a cross-sectional view in the tire meridian direction.
The contact point between the tangent line L1 that is in contact with the innermost layer in the tire radial direction and the innermost and outermost wire cross sections in the tire width direction from the rim fitting surface side in the wire arrangement structure and the tangent line L1 with respect to the outermost wire cross section. C2 is defined and
Any of claims 1 to 14, wherein the gauge G2 in the tire radial direction from the contact C2 to the rim fitting surface and the outer diameter φ of the bead wire have a relationship of 1.3 ≦ G2 / φ ≦ 9.5. Pneumatic tires listed in one.

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